Method of welding



Jan. 14, 1964 J. LIPPART ETAL METHOD OF WELDING 4 Sheets-Sheet 1Original Filed March 19, 1957 QQQ Fig.2. I

LY IT POWER S ING TAPER 4 WELD RENT Fig. 4.

Fig. l.

SEQUENCE TIMER (EUR CONTROL UNIT Jan. 14, 1964 J. LIPPART ETAL memos 0FWELDING 4 Sheets-Sheet 2 Original Filed March 19, 1957 3 Fig.5.

Jan. .14, 1964 .1. LIPPART ETAL mmuon 0F WELDING bSheets-Sheet 3Original Filed March 19, 1957 ZOI 23 Fig. l4.

J 14, 1964 J. LIPPART ETAL METHOD OF WELDING 4 Sheets-Sheet 4 OriginalFiled March 19. 1957 United States Patent 3,118,052 METHUD 0F WELDINGJohn Lippart, Prospect Park, and Alfred W. Klein, Pittsburgh, Pa,assignors to Westinghnuse Electric Corporatlon, East Pittsburgh, Pa., acorporation of Pennsyivania @riginal application Mar. 19, 1957, Ser. No.647,057, now Patent No. 3,062,949, dated Nov. 6,. 1962. Divided and thisapplication Oct. 20, 1959, Ser. No. 847,546

16 Claims. (Cl. 219-137) This invention relates to the art of weldingand has particular relationship to the welding of tubes to a sheet orplate. This application is a division of application Serial No. 647,057,filed March 19, 1957, now Patent No. 3,062,949.

The necessity of joining tubes to a sheet arises particularly in themaking of such apparatus as condensers and heat exchangers for powergenerators and refrigerating apparatus. In certain such apparatus, it isnecessary that the joints between the tubes and the sheet shall begastight seals to avoid leakage of the heating or cooling medium. Thisrequirement is of particular importance in heat exchangers for powergenerators of the atomic or nuclear type, since leakage in suchapparatus would cause radio-active material to flow into the turbinesdestroying the usefulness of the turbines.

Noble Patent 1,508,711 in FIG. 12 discloses an arrangement for welding aflue 118 to a flue sheet 117 and typifies the prior art. Apparatus basedon Nobles teaching when applied to the welding of tubes to a tube sheetby rotating a welding electrode about the tube has provedunsatisfactory. Welds produced in this way were found to be leaky.Another practice which has been in Vogue in sealing tubes to sheet is toinsert the tubes in the sheet and to produce the seals by passing overthe array of junctions between the tubes and the sheet by hand With awelding electrode of the rod type. Because of the number of tubes whichare to be joined to each sheet, this procedure has proved highly costly.The making of a single heat exchanger in one situation has cost as muchas $100,000.

It is accordingly broadly an object of this invention to provide a lowcost method for joining a tube to a tube sheet or plate.

This invention in its broader aspects arises from the realization thatlow cost apparatus for joining tubes to a sheet should includefacilities for moving-rotating in the case of a cylindrical tubeawelding electrode about the axis of the tube while the electrode iscentering in the tube. It is further realized that Noble suggests suchmovement, but the Noble apparatus is not satisfactory because it lacksthe necessary precision. The wall of each tube of such apparatus as aheat exchanger is relatively thin, and because the Noble electrodecannot be maintained precisely positioned relative to the joint to bewelded as it is moved around the joint, attempts to weld tubes to sheetwith appartaus such as disclosed by Noble results in frequentperforation of the tubes. This is one of the principal causes of theleaking joints.

It is accordingly another object of this invention to provide alow-labor-cost method for joining tubes of relatively small thickness toa tube sheet by welded seals which shall be gas-tight in the practice ofwhich an electrode shall be moved around the joints between the tubesand the sheet.

In accordance with this invention, the welding of a tube to a sheet iscarried out with a nonconsumable electrode which is positioned on amandrel positioned axially in the tube. In the practice of thisinvention, the sheet is provided with a shoulder around each opening inwhich a tube is to be sealed, for example, by trepanning after theopening is cut into the sheet. The tube is then inserted in the opening,for example, by rolling in a position such that the shoulder firmlyengages the surface of the tube. The electrode is positioned at apredetermined first angle with reference to the axis of the tube, at apredetermined second angle with reference to the successive planesdefined by the axis of the tube and the successive points at which awelding are from the electrode terminate and perpendicular to the planeof the opening in the sheet through which the tube projects and at apredetermined distance from the outer edge of the shoulder of the sheetwhich engages the tube. The electrode is then moved around the shoulderwhile remaining precisely positioned with respect to the axis of thetube and shoulder as just described, and a welding arc is fired betweenthe electrode and the shoulder so that as the electrode is moved awelded seal is produced. The spacing between the electrode and the outerrim of the shoulder must be such that during this movement the arc burnscontinuously and quietly. The electrode is moved continuously about theaxis of the tube through an angle somewhat greater than 360 so thatthere is an overlap at the point where the welding started. The movementaround the joint is now continued while the Welding current is decreasedor tapered oif until the arc is interrupted. The tapering off precludesthe formation of a crater. It has been found that the practice of thismethod leads to a joint between the tube and the sheet which is gastightand the tube is not perforated during the welding operation.

Where a joint substantially longer (longitudinally along the tube) thanthat which can be produced by fusing the shoulder to the sheet isnecessary, a ring of filler material may be placed about the tube justabove the shoulder, and this filler material may be fused into the weldjust described after the latter Weld is formed by moving the electrodepositioned as just described around the filler ring in the same manneras it was moved around the shoulder. Where the tubes and the sheet areof different materials, a filler material capable of fusing to each ofthe dilferent materials may be initially placed about the joint of thetube, and the sheet and the filler material may be fused to form a sealby moving the electrode in the manner just described.

The novel features considered characteristic of this invention aredescribed generally above. The invention itself both as to itsorganization and its method of operation, together with additionalobjects and advantages thereof will be understood from the followingdescription of preferred embodiments taken in connection with the acconipanying drawings, in which:

FIGURE 1 is a fragmental view partly in side elevation and partly insection of a heat exchanger produced in the practice of this invention;

FIG. 2 is a fragmental view in top elevation of the heat exchanger shownin FIG. 1;

FIG. 3 is a fragmental view in section showing the relationship betweenthe thickness of a tube and the weld produced in sealing the tube in aheat exchanger of the type shown in FIG. 1;

FIG. 4 is a diagrammatic view showing welding apparatus used in thepractice of this invention;

FIG. 5 is a view partly in section and partly in side elevation of awelding gun or torch used in the practice of this invention;

FIG. 6 is a view in side elevation of an electrode supporting body unitincluded in the apparatus shown in FIG. 5';

FIG. 7 is a view in top elevation of this body;

PEG. 8 is a view in side elevation of an adapter co operative with thebody shown in FIG. 6 to support the welding electrode included in theapparatus shown in FIG. 5;

FIG. 9 is a view in top elevation of the adapter shown in FIG. 8;

FIG. 10 is a view in side elevation of a holder included in theapparatus-shown in FIG. 5;

FIG. 11' isa View shown in top elevation of this electrode holder;

FIG; 12 is a view in side elevation of the apparatus shown in PK 5 whichshows the relationship maintained between the electrode and the tube andsheet in making a weld between the tube and the sheet in a typicalsituation;

FIG. 13 is a view in top elevation showing the tube and a gage forpositioning the electrode in welding a tube to a sheet in the practiceof this invention;

FIG. 14 is a view in section taken along line XIVXIV of FIG. 13;

FIG. 15 is a view in side elevation of a wire gage used in positioningthe electrode in cooperation with the apparatus shown in F168. 13 and14; and

FIG. 16 is a view in part elevation of the gage shown in FIG. 15.

FIGS. 1 and 2 show in rudimentary form a heat exchanger to the making ofwhich this invention is applicable. The heat exchanger includes a blockor sheet 21 of a material, such as stainless steel, for example No. 347stainless steel. The exchanger also includes a plurality or" U-shapedtubes 23, the ends 25 of which pass through openings 27 in the block.These tubes are also composed of stainless steel, such as No. 347, andare relatively thin. The ends 25 of the tubes 23 are sealed in' theopenings 27 by are welded joints 29 and it is essential that the jointsbe gas tight.

FTG. 3 shows the principal specifications for each weld. It is necessarythat the weld shall not penetrate through the wall and shall have alength of the order of one and one-half times the thickness of thesheet.

The apparatus with which the welding is carried out is shownschematically in FIG. 4. This apparatus includes a Gun, a Gas SupplyUnit, a Power Supply Unit, a high frequency stabilizer, labelled H. F.Stabilizer, a Welding Current Taper Control Unit and a Sequence Timer.

The Gun is of the non-consumable electrode gasshielded type and iscapable of being rotated about the joint between the tube 23 and theplate or sheet 21 during the welding operation.

The Gun (FIGS. 511) includes a mandrel 31, an electrode supporting bodyunit 33 (FIGS. 5, 6 and 7) mounted rotatably on the mandrel 31, anadapter 35 (FIGS. 5, 8 and 9) mounted on the body unit 33:, a holder 37(FIGS. 5, l0 and 11) mounted in the adapter 35, a nonconsumable weldingelectrode 39 held by a head screw 41 which engages the holder 37, and aceramic cup 43 held by the holder 37 through which the electrode 41extends and through which shielding gas passes. The body unit 33 isdriven by a motor 45 through a flexible. shaft 47 thus causing theelectrode 41 to rotate about the mandrel 31.

The mandrel 31 is of elongated generally cylindrical form and has a tip51, an attenuated supporting end 53 and a central section 55. The tip 51includes a shoulder 57 from which extend fingers 59 formed by crossslots 61 longitudinally of the tip 51 to the shoulder 57. The fingers 59have knobs 63. The shoulder 57 is terminated by a flange 65. The centralsection includes an attenuated stub 71 terminated by another shoulder73. The shoulder 73 is adapted to be engaged by a fork for removal ofthe mandrel 31 from the tube 23 after a welding operation. The mandrel31 is preferably composed of copper.

The fingers 59 of the mandrel 31 are resilient so that the mandrel maybe readily slipped into a tube 23. Once in the tube, the fingers 59engage the tube wall so that the mandrel 31 is held firmly. When themandrel is.

slipped into a tube 23, the flange engages the rim of the tube.

The body unit 33 includes a sleeve 81 and a clamp 83 and may be composedof an insulating material such as a phenolic condensation product. Thereis an elongated opening 35 through the sleeve which is provided with abushing 87 of a metallic material such as hot-rolled steel. The openingterminates in an internally threaded end 39 of greater diameter. A bolt91 of insulating'rmaterial such as a phenolic condensation product isscrewed into the end 59 and is secured to the sleeve 31' by a nut 93.The head 95 of the bolt 91 is slotted at the top and has a. receptacle97 for engaging the end of the flexible shaft 47. The bolt 91 isprovided with a cylindrical seat 99 in its end; this seat 99 engages theend 53 of the mandrel. The vertical position of the electrode 39 may beset withinlimits by screwing the bolt'i ll in or out.

The clamp 33 extends integrally from the sleeve 81 and includes a blockof generally trapezoidal form. A circular opening 151 extends partlythrough the block and partly through the body of the sleeve 81. A slot103 extends transversely through the block to the opening. 101 andanother slot 16 5 extends from the opening 101 through a portion of thebody of the sleeve 81 and the junction of the block and the sleeve.There is a hole 107 transversely through the block adapted to pass abolt 109 which may be secured by a nut 111 engaging the bolt on the sideopposite the head.

The adapter 35 (FIGS. 8 and 9) may be composed of brass and is in theform of aright-angle bracket made up of two arms 12 1 and 123 weldedtogether. The arm 12 1 is terminated by a cylindrical tip 125, the axisof which is at an angle to the axis of the arm. This tip has an opening127 therethrough, a portion of the opening being of greater diameterthan the remainder. The other arm 123 is provided with an externalthread 129 adapted to engage a nipple (not shown) of a conductor from ashielding gas supply through which shielding gas may be transmittedthrough the bracket. There is an opening 131 extending continuouslythrough the arms 121 and 123 of the adapter 35 and communicating withthe opening 127 in the tip 125. This opening is beveled at the end ofthe arm 123 from which it extends to accommodate the nipple.

The holder 37 (FIGS. 10 and 1:1) is also in the form of a right anglebracket having a central block section 141- from which projections 143and 145 extend. An opening 1'47 extends through the block 141 and theprojection 143- and terminates in an attenuated end 149 having adiameter such that the electrode 39 fits in it neatly. The opening 147has an internal thread 151 at the end remote from the tip 149. Theprojection 143 has a threaded shoulder 153 from which a beveled tip 155extends. The tip 155' is provided with four peripheral holes 157 in theportion adjacent the shoulder 153. The internal thread 151 is such as toengage the head screw 41 in which the electrode 39 is secured and thethread 153 is such as to engage a cooperative thread of a ceramic cup 43through which shielding gas passing, through the openings 157 may flow.When the head screw 41 carrying the electrode 39 is screwed into theopening 151 in the block 141, the electrode 39 extends through the blockand through the cup 43. The other projection 145 includes a pair ofshoulders 161 and 163 of progressively decreasing diameter from which athreaded tip 165 extends. There is an opening 167 in the shoulder 161which communicates with the opening 147 in the block 141 and withlateral openings 169 in the shoulder 163. The opening 167 may be boredas a continuation of an opening through the block 141 and the part ofthe opening in the block 141 above opening 147 may be plugged. Theprojection 145 is set in the opening 127 with the shoulder 161 engagingthe wall of the opening 127 and the opening 131 in communition with theopening 169. The threaded tip 165 is adapted to pass through the narrowpart of the opening 127 in the adapter and a nut may be screwed on thetip 165 to secure the holder. Gas which enters the opening 131 flowsthrough the openings 169, 167, 147 and 157 into the cup 43.

In the assembled Gun, the arm 121 of the adapter 37 from which thecylindrical tip 125 extends is held by the clamp 83 of the body unit 33.For this purpose, the arm 121 is passed through the opening 101 in theclamp and is pinched by the opening when the nut 11-1 is screwed ontothe bolt. The arms 121 and 123 of the adapter 35 are formed in twopieces to facilitate the as sembly of the Gun. Arm 12 1 is first slippedinto the clamp 83 and then arm 123 is joined to it by welding. Theangular position of the adapter 35 about the axis of the clamp opening101 may be set by releasing the bolt 109 and rotating the arm 121 to thedesired position.

The Power Supply Unit may be of any suitable type available in the artbut should preferably have facilities for readily varying the weldingcurrent during the welding operation so that the current may be taperedoff at the end of a weld. Such facilities may preferably include asaturable reactor (not shown) in the Power Supply Unit, the saturationof which may be readily varied during welding by changing the resistanceof a variable resistor.

The RF. Stabilizer may be of any suitable type available in the art butmust operate in such a manner as to avoid radio interference, asrequired by the Civil Aeronautics Authority. The HP. Stabilizer isconnected in circuit with the electrode 39 and work 21 and whenenergized produces a high frequency spark (or field) between theelectrode 39 and work 21-23 to fire an arc.

The Sequence Timer may be of any suitable type but preferably should beof the type disclosed in an application, Serial No. 647,007, filedconcurrently herewith by Austin Dixon, and assigned to WestinghouseElectric Corporation. This Sequence Timer should include facilities fortiming the following sequences: (1) The flow of inert gas is started toprepurge the arc. (2) A predetermined time interval following the startof the prepurge, the Power Supply Unit and the HF. Stabilizer areenergized to fire the arc. (3) After the arc is fired motor 45 fordriving the Gun is energized. (The motor 45 may also be energizedsimultaneously With the Power Supply Unit and the HF. Stabilizer.) (4) Apredetermined time interval after the operation in item 2, the highfrequency unit may be turned off (this is optional). (5) After a timeinterval sufiicient to permit the Gun to rotate through an angle greaterby a small magnitude than 360, the Welding Taper Current Control Unit isactuated and the current supplied by the power supply unit is graduallytapered off. The tapering may be at a predetermined rate and for apredetermined time suitable for the material being welded. (6) At theend of the taper interval the arc is extinguished. (7) The gas continuesto flow for a predetermined time interval after the arc is extinguishedto post purge the weld and then the flow of gas is stopped.

The Welding Current Taper Control Unit may be of any suitable type andspecifically of the type disclosed in the above-mentioned Dixonapplication. When actuated, it causes the saturation of the reactor inthe Power Supply Unit to vary or to produce the taper desired.

The projection from which the threaded tip extends may be rotated in theopening .127 in the adapter bracket to a desired position and locked inthis position by the nut. The angular position of the electrode withreference to the axis of the material may thus be set.

The invention will be described as used in a typical practical situationin which tubes 23 having a diameter of /8 inch and a thickness of .050inch are to be welded into a sheet or plate 21 having a thickness of theorder of six inches. Tubes have been welded in plates having thicknessesof as high as 18 inches in the practice of this invention. in this caseuniform circular ring welds 29 having a height of .075 and a thicknessso as not to perforate the tube 23 are to be made. Preparatory to thewelding operation, the openings 27 in which the tubes 2-3 are to bewelded are bored in the sheet or plate 21 to the desired dimensions. Inaddition, a trepanning operation is carried out so that there is ashoulder 151 around each opening (see FIG. 1).

Each tube 23 after being thoroughly degreased by washing with a suitablechemical such as trichloroethylene, is rolled into the associatedopening 27 in the sheet 21 or plate. In carrying out the rollingoperation every precaution should be taken to prevent grease frompenetrating into the junction between the tube 23 and the plate 21.Additional degreasing operations may then be carried out on the tubesand the plate after the rolling of all tubes into the plate.

When a tube 23 is rolled into the opening 27 in the sheet 21, theshoulder 151 bounds the tube near its upper end. In a typical situationthe shoulder 151 is of the order of of an inch below the upper rim ofthe tube 21. After the degreasing, a ring 153 of filler material isdisposed on each tube just above the junction between the tube 23 andthe plate 21.

The mandrel 31 is then slipped into a tube 21 to a position at which itsflange '65 engages the upper rim of the tube. The mandrel 31 fits snuglyin the tube 21. The remaining portion of the torch or Gun is then placedon mandrel end 53 with the sleeve encircling the end of the mandrel andthe top of the mandrel engaging the seat 9% in the bolt 91. The flexibleshaft 47 is engaged in the receptacle 7 of the bolt 91.

The Gun is now adjusted to the proper position as shown in FIG. 12. Forthe setting of the Gun the apparatus shown in FIGS. 13 through 16 may beused. This apparatus includes a sleeve gage and a wire gage. The sleevegage includes a semicircular sleeve 2 01 having a shoulder 203. The gagehas a wire handle 205 by means of which it may be positioned. The wiregage includes a fiat wire 211 having a loop handle 213 at one end and anotched tip 215 bent at an angle at the other. The sleeve gage is heldon the shoulder 151, and the electrode 39 is set so that its tip restsbetween the shoulder 203 of the sleeve gage and its adjacent neckportion 216. The holder 37 is turned in the opening 127 in the adapter35 until the electrode is at the desired angle to the axis of the tube.After this operation is carried out for a situation as illustrated inFIG. 12, the electrode 3h is at an angle in trailing relationship ofabout 18 to the axis of the tube 23 and is a distance of the order of.025 from the outer edge of the shoulder 151. The adapter 37 may now beturned in the clamp opening 101 until the electrode 29 is at a trailingangle of about 3 to 5. The position of the electrode 39 may be checkedby the wire gage 211.

In the illustrated situation, the electrode 39 is of the thoriatedtungsten type and has about 1 to 2% thorium. The body of the electrodehas the diameter of inch which tapers to about .030 inch at the tip.

After the electrode has been set as just disclosed,

the starting switch (not shown) of the Sequence Timer is actuated, and awelding operation is carried out. in the typical situationillustratedthe prepurging gas should be a mixture of argon and helium,the argon being supplied at therate or" to 6cubic feet per hour andhelium at 9 to 10 cubic feet per hour. The prepurging operation shouldtake about three seconds i one second. At the end of the prepurgingoperation, the Power Supply Unit and the Stabilizer are energizedimmediately causing an arc to be fired between the electrode 3% and theshoulder 151-. The flow of welding current then starts the drive motor45 which rotates the electrode about the vndrel, in the typicalsituation illustrated at a rate of about 1 to 1 /8 revolutions perminute. The welding current in this situation is of the order of 80 to85 amperes and the arc voltage of the order of 10 to 12 volts directcurrent straight polarity.

After the arc is tired, the welding operation then procoeds. During theoperation the Stabilizer may be turned off, for example 5 seconds 1- onesecond after the arc is fired. The electrode rotates through an angleor" about 375i5, and after it reaches this-angle the welding current isgradually tapered to suppress any crater formation. The tapering takesabout six seconds i one second. The rotation continues during thetapering interval and stops when the how of welding current stops. Theflow of inert gas then continues for five seconds 1 two seconds toproduce the postpurging operation.

The lower portion of the weld 27 shown in FIG. 3 is thus produced. Inmany situations the weld is now complete; in others it is necessary thata ring 153 be fused into the joint or seal. In such situation theelectrode is reset to a position opposite the outer rim of the ring 153and then a second welding operation as described above is carried out.The ring is then fused into the weld produced by the first weldingoperation. A weld as shown in FIG. 3 is then completed.

The above described operation has been used repeatedly to produce soundgas-tight-welds as required. With the apparatus disclosed herein and bythe practice of the method in accordance with this invention, such weldsmay be produced in large numbers at a low cost compared to the cost ofproducing the same welds by the prior art methods mentioned.

One of the important features of this invention is that the Gun iscompact. In actual practice it is so compact that it can swing inside ofa radius of 1 /8 inch. This gives the Gun axis to make seal welds incorners and in situations where the weld is made near a wall.

While preferred embodiments of this invention have been disclosedherein, many modifications thereof are feasible. For example, insituations in which the tube 23 and sheet 21 are of dissimilar materialsthe shoulder 151 may be replaced by a ring or filler of a material whichfuses both with the material of tube 23 and the material of the sheet21. This invention then is not to be restricted except insofar as isnecessitated by the spirit of the prior art.

We claim as our invention:

1. The method of making a gas-tight joint between a tube and sheet, saidsheet having an opening into which said tube is to project, and saidsheet and said tube being of dissimilar materials, by arc-welding with anonconsumable electrode which comprises, positioning said tube in saidopening, placing a ring of a filler material which produces satisfactoryjoints between said dissimilar materials around said tube at a positionadjacent said sheet, positioning said electrode at a predetermined firstangle to the axis of said tube, at a predetermined second angle intrailing relationship to the successive planes perpendicular to theplane of said opening and including the axis of said tube and thesuccessive points where a welding are from said electrode is toterminate and with the tip of said electrode a predetermined distancefrom the outermost point of said ring such that a continuous quietwelding arc may be maintained between said electrode and said ring,moving said electrode about said axis while maintaining said electrodeso positioned, and producing a welding are between said electrode andsaid ring while said electrode is being so moved to weld said ring andproduce a seal between said tube and sheet at said junction, the jointproduced by said weld including only the metal of said ring, the metalof said tube and the metal of said sheet.

2. The method of making a gas-tight precision joint between a tube andsheet, said sheet having an opening into which said tube is to project,by arc-welding with a non-consumable electrode which comprisestrepanning said sheet around said opening to provide a shoulder in saidsheet around said opening, positioning said tube in said opening,positioning said electrode at a predetermined first angle to the axis ofsaid tube, at a predetermined second angle to the successive planesperpendicular to the plane of said opening and including the axis ofsaid tube and the successive points where a welding are from saidelectrode is to terminate and with the tip of the electrode apredetermined distance from the top of said shoulder, moving saidelectrode about said axis while maintaining said electrode sopositioned, and producing a welding are between said electrode and saidshoulder while said electrode is being so moved to weld said shoulder tosaid tube, the joint produced by said weld including only the metal ofsaid shoulder and the metal of said tube, the current of said are beingmaintained at a mag.- nitude such as to fuse the metal of said shoulderand tube while said electrode traverses an angle about said axis ex-vceeding 360 by a small magnitude and thereafter while said electrodecontinues to move about said axis said current is tapered from saidmagnitude to zero magnitude at a predetermined rate.

3. The method of making a gas-tight joint between a tube and sheet, saidsheet having an opening into which said tube is to project, byarc-welding with a nonconsumable electrode, which comprises positioningsaid tube in said opening providing shoulders in said sheet around saidopening, positioning said electrode at a predetermined first angle tothe axis of said tube, at a predetermined second angle in trailingrelationship to the successive planes perpendicular to the plane of saidopening and including the axis of said tube and the successive pointswhere a welding are from said electrode is to terminate and with the tipof the electrode a predetermined distance from the top of said shoulderand spaced a substantially greater distance than said predetermineddistance from said tube, moving said electrode about said axis whilemaintaining said electrode so positioned, and producing a welding arcbetween said electrode and said shoulder while said electrode is beingso moved to weld said shoulder to said tube, the joint produced by saidweld including only the metal of said shoulder and the metal of saidtube.

4. The method of making a gas-tight joint. between a tube and sheet,said sheet having an opening into which said tube is to project, byarc-welding with a nonconsumable electrode, which comprises positioningsaid tube in said opening with a portion of said tubeextending out ofsaid opening in the direction from which the welding arc is to beproduced, providing a shoulder in said sheet around said portion, saidportion extending beyond said shoulder in the direction from which saidare is to be produced, setting said electrode in a predeterminedposition with respect to said tube and shoulder, moving said electrodeabout said shoulder while maintaining said electrode so positioned, andproducing a welding are between said electrode and said shoulder whilesaid electrode is being so moved to weld said shoulder to said tube inthe region of said portion, said electrode being spaced from said tubeand shoulder so that during welding said shoulder is fused and the partof said portion of said tube extending beyond said shoulder in saiddirection is substantially unaffected, the joint produced by said weldbeing in said portion in the region thereof adjacent said sheet andincluding only the metal of said shoulder and the metal of said tube inthe region of said portion, said shoulder being so dimensioned and theparameters of said welding being such that the weld filet haspredetermined dimensions and penetrates only partly through saidportion.

5. The method of making a gas-tight joint between a tube and sheet, saidsheet having an opening into which said tube is to project, said jointto be made by arc-welding with a non-consumable electrode, said methodcompris ing positioning said tube in said opening, providing a shoulderin said sheet around said opening, setting said electrode in arc weldingposition with respect to said tube and shoulder, said electrode beingnear the outer rim of said shoulder and spaced a substantially greaterdistance from said tube, moving said electrode about the axis of saidtube while maintaining said electrode so set, and producing a weldingare between said electrode and said shoulder while said electrode isbeing so moved to weld said shoulder to said tube, the joint produced bysaid Weld including only the metal of said shoulder and the metal ofsaid tube, said shoulder being so dimensioned and the welding beingcarried out with parameters such that the weld filet has predetermineddimensions and that said let does not penetrate inwardly through thewall of said tube.

6. The method of making a gas-tight joint between a tube and sheet, saidsheet having an opening into which said tube is to project, said jointto be made by arc-weld ing with a non-consumable electrode, said methodcomprising positioning said tube in said opening, with a portion of saidtube extending out of said opening in the direction from which thewelding arc is to be produced, providing a shoulder in said sheet aroundsaid opening, said tube having a portion extending beyond said shoulderin the direction from which the welding arc is to be produced, with therim of said last-named extending portion serving as a reference surfacesetting said electrode in a predetermined position with respect to saidtube and shoulder, moving said electrode about the axis of said tubewhile maintaining said electrode so positioned and with said rim stillserving as a reference surface, and producing a welding arc between saidelectrode and said shoulder while said electrode is being so moved toWeld said shoulder to said tube, said electrode being spaced from saidtube and shoulder so that during welding said shoulder is fused and thepart of said portion of said tube extending beyond said shoulder in saiddirection is substantially unaffected, the joint produced by said weldbeing in said portion substantially in the region thereof adjacent saidsheet and including only the metal of said shoulder and the metal ofsaid tube, said shoulder being so dimensioned and the welding beingcarried out with parameters such that the weld filet has predetermineddimensions and that said filet does not penetrate inwardly through thewall of said tube.

7. The method of making a gas-tight joint between a tube and sheet, saidsheet having an opening into which said tube is to project, said jointto be made by arc-welding with a non-consumable electrode, said methodcomprising positioning said tube in said opening, providing a shoulderin said sheet around said opening, setting said electrode in apredetermined position with respect to said tube and shoulder, the tipof said electrode when so positioned being near the outer rim of saidshoulder and spaced a substantially greater distance from said tube,moving said electrode about said shoulder while maintaining saidelectrode so positioned, and producing a welding arc between saidelectrode and said shoulder while said electrode is being so moved toweld said shoulder to said tube, the joint produced by said weldincluding only the metal of said shoulder and the metal of said tube,said shoulder being so dimensioned and the parameters of said weldingbeing so set that the weld filet has predetermined dimensions and thatsaid filet extends into said tube but does not penetrate inwardlythrough the wall of said tube.

8. The method of making a gas-tight joint between a tube and sheet, saidsheet having an opening into which said tube is to project, said jointbeing made by arc-welding with a non-consumable electrode, said methodcomprising positioning said tube in said opening, providing a shoulderin said sheet around said opening by placing a ring of filler materialaround said tube encircling said opening, said tube having a portionextending beyond said shoulder in the direction from which said weldingarc is to be produced setting said electrode in arc welding positionwith respect to said tube and shoulder, moving said electrode about theaxis of said tube while maintaining said electrode so set, and producinga welding are between said electrode and said shoulder while saidelectrode is being so moved to weld said shoulder to said tube, saidelectrode being spaced from said tube and shoulder so that duringwelding said shoulder is fused and the part of said portion of said tubeextending beyond said shoulder in said direction is substantiallyunaffected, the joint produced by said weld being substantially in saidportion in the region thereof adjacent said sheet and includingsubstantially only the metal of said ring and the metal of said tube,said ring being so dimensioned and positioned and the welding beingcarried out with parameters such that the weld filet has predetermineddimensions and that said filet penetrates substantially inwardly intothe wall of said tube but does not penetrate inwardly through the wallof said tube.

9. The method of making a gas-tight precision joint between a tube andsheet, said sheet having an opening into which said tube is to project,said joint to be made by arcwelding with a non-consumable electrode,said method comprising trepanning said sheet around said opening toprovide a shoulder in said sheet around said opening, positioning saidtube in said opening, positioning said elec trode at a predeterminedfirst angle to the axis of said tube, at a predetermined second angle intrailing relationship to the successive planes perpendicular to theplane of said opening and including the axis of said tube and thesuccessive points where a welding are from said electrode is toterminate and with the tip of the electrode a predetermined distancefrom the top of said shoulder and spaced a substantially greaterdistance from said tube, moving said electrode about said axis whilemaintaining said electrode so positioned, and producing a welding arcbetween said electrode and said shoulder while said electrode is beingso moved to weld said shoulder to said tube, the joint produced by saidweld including substantially only the metal of said shoulder and themetal of said tube, and the welding are parameters and said first andsecond angles, said distance and the dimensions of said shoulder beingso set that the weld filet forming said joint has the dimensionsrequired.

r10. The method of making a gas-tight precision joint between a tube andsheet, said sheet having an opening into which said tube is to project,said joint to be made by arc-welding with a non-consumable electrode,the said method comprising trepanning said sheet around said opening toprovide a shoulder in said sheet around said opening, positioning saidtube in said opening, positioning said electrode at at predeterminedfirst angle to the axis of said tube, at a predetermined second angle intrailing relationship to the successive planes perpendicular to theplane of said opening and including the axis of said tube and thesuccessive points where a welding are from said electrode is toterminate and with the tip of said electrode a predetermined distancefrom the outer rim of said shoulder and spaced a substantially greaterdistance than said predetermined distance from said tube, said distancebeing such that a continuous quiet welding arc may be maintained betweensaid electrode and said rim, moving said electrode about said axis whilemaintaining said electrode positioned as aforesaid, and producing, awelding arc between said electrode and said shoulder while saidelectrode is being so moved to weld said shoulder to said tube, thejoint produced by said weld including only the metal of said shoulderand the metal of said tube and the welding arc parameters and said;first and second angles, said distance, and the dimensions of saidshoulder being so set that the weld filet forming said joint has thedimensions required.

11. The method of making a gas-ti ht precision joint between a tube andsheet, said sheet having an opening into which said tube is to project,said joint to be made by arc-welding with a non-consumable electrode,the said method comprising trepanning said sheet around said opening toprovide a shoulder in said sheet around said opening, positioning saidtube in said opening, positioning said electrode at a predeterminedfirst angle of the order of 18 to the axis of said tube, at apredetermined second angle of the order of 3 to 5 to the successiveplanes perpendicular to the plane of said opening and including the axisof said tube and the successive points where a welding are from saidelectrode is to terminate and with the tip of said electrode apredetermined distance from the outer rim of said shoulder, saiddistance being such that a continuous quiet welding arc may bemaintained between said electrode and said rim, moving said electrodeabout said axis while maintaining said electrode so positioned and withsaid second angle trailing the rotation, and producing a welding arcbetween said electrode and said shoulder while said electrode is beingso moved to weld said shoulder to said tube, the joint produced by saidweld including only the metal of said shoulder and the metal of saidtube, and said shoulder being so dimensioned and said welding havingparameters being such that the weld filet of said joint has the requireddimensions.

12. The method of making a gas-tight joint between a tube and sheet,said sheet having an opening into which said tube is to project, saidjoint to be made by arc-welding with a non-consurnable electrode, thesaid method comprising positioning said tube in said opening, with aportion of said tube extending out of said opening in the direction fromwhich the welding arc is to be produced, with the rim of said extendingportion serving as a reference surface setting the distance of saidelectrode from the junction between said tube and opening, setting theangle of said electrode to said tube and junction and moving saidelectrode about the axis of said tube while maintaining said electrodeso positioned and with said rim still serving as a reference surface,and producing a welding are between said electrode and said junctionwhile said electrode is being so moved to weld said tube to said sheetat said junction, said electrode being spaced from said tube andshoulder so that during welding said shoulder is fused and the part ofsaid portion of said tube extending beyond said shoulder in saiddirection is substantially unaffected, the joint so produced beingsubstantially in said portion adjacent the region of said sheet.

13. The method of making a gas-tight joint between a tube and, sheet,said sheet having an opening into which said tube is to project, byarc-welding with a non-consumable electrode, which comprises positioningsaid tube in said opening, providing a shoulder in said sheet aroundsaid opening, setting said electrode in a predetermined position withrespect to said tube and shoulder with the tip of said electrodeadjacent the outer rim of said shoulder and spaced at substantiallygreater distance from said tube,.moving said electrode about the axis ofsaid tube while maintaining said electrode so positioned, and producinga welding are between said electrode and said shoulder while saidelectrode is being so moved to weld said shoulder to said tube, thejoint produced by said weld including only the metal of said shoulderand the metal of said tube, said shoulder being so dimensioned and thewelding being carried out with parameters such that the weld filet haspredetermined dimensions, extends a substantial distance into said tubebut does not penetrate inwardly through said tube.

14. A method of providing by arc welding a weld connection between atube and a tube sheet of high strength comp-rising the steps of mountingsaid tube in said sheet with a portion of said tube extending eyond saidsheet in the direction from which the welding arc is to be app issupporting an electrode in spaced relationship to the tube and the tubesheet to be welded together, rotating the electrode in a circular pathabout the tube to be welded, supplying sufficient electric current tosaid electrode as the electrode rotates about the tube to be welded toeffect the melting of the tube sheet to a depth necessary to provide ahigh strength weld and melt part of the tube wall, said electrode beingspaced from said tube and shoulder so that during-welding said shoulderis fused and the part of said portion of said tube extending beyond saidshoulder in said direction is substantially unaffected, said melted partof said wall being in said portion adjacent the joint of said portionand the tube sheet during the welding, passing inert gas to theelectrode to provide for welding in an inert gas atmosphere, and aftersaid weld is formed interrupting the supply of said current, andthereafter flowing said inert gas adjacent the tube in the region of theweld, said gas being deflected around the weld by said portion.

15. The method of making by arc welding a gas-tight joint between a tubeand sheet, said sheet having an opening into which said tube is toproject, said joint to be made by arc-welding with a non-consumableelectrode, said method comprising positioning said tube in said opening,providing a shoulder in said sheet around said opening, a portion ofsaid tube extending beyond said shoulder in the direction from which thewelding arc is to beproduced, setting said electrode in arc weldingposition with respect to said tube and shoulder, moving said electrodeabout the axis of said tube while maintaining said electrode so set,producing a welding are between said electrode and said shoulder whilesaid electrode is being so moved to weld said shoulder to said tube,said electrode being spaced from said tube and shoulder so that duringwelding said shoulder is fused and the part of said portion of said tubeextending beyond said shoulder in said direction is substantiallyunaffected, shielding said arc in a protective gas, after said Weld hasbeen produced interrupting said are, and after said are has beeninterrupted continuing to supply said protective gas for predeterminedinterval of appreciable duration, said lastnamed gas being deflectedaround said weld by said portion, the joint produced by said weld beingsubstantially in said portion in the region thereof adjacent said sheetand including only the metal of said shoulder and the metal of saidtube, said shoulder being so dimensioned and the welding being carriedout with parameters such that the weld filet has predetermineddimensions, penetrates substantially inwardly into the wall of saidtube, but does not penetrate inwardly through the Wall of said tube.

16. The method of making a gas-tight joint between a tube and sheet,said sheet having an opening into which said tube is to project, saidjoint to be made by arc-welding with a non-consumable electrode, saidmethod comprising positioning said tube in said opening, providing ashoulder in said sheet around said opening, a portion of said tubeextending beyond said shoulder in the direction from which the weldingarc is to be produced, setting said electrode in arc welding positionwith respect to said tube and shoulder, moving said electrode about theaxis of said tube while maintaining said electrode so set, producing awelding are between said electrode and said shoulder while saidelectrode is being so moved to weld said shoulder to said tube, saidelectrode being spaced from said tube and shoulder so that duringwelding said shoul- 13 der is fused and the part of said portion of saidtube extending beyond said shoulder in said direction is sub stantiallyunaffected, shielding said arc in a protective gas, after said Weld hasbeen produced interrupting said arc and interrupting the movement ofsaid electrode, and after said are has been interrupted continuing tosupply said protective gas for a predetermined interval of appreciableduration, the weld produced being in the region of said portion near thejoint thereof with said sheet and said portion deflecting saidlast-named protective gas around 10 said Weld.

References Cited in the file of this patent UNITED STATES PATENTS874,084 Iottrand et a1. Dec. 17, 1907 14 Sch-ickert May 30, 1911 ZuckJuly 17, 1917 Rose Jan. 7, 1941 Behnke et al. June 6, 1950 Tyrner et a1.Aug. 8, 1950 Pilia et a1 Dec. 31, 1957 Apblett et a1. Oct. 13, 1959Edens et a1. Apr. 19, 1960 OTHER REFERENCES Welding Handbook, thirdedition, published by the American Welding Society.

1. THE METHOD OF MAKING A GAS-TIGHT JOINT BETWEEN A TUBE AND SHEET, SAIDSHEET HAVING AN OPENING INTO WHICH SAID TUBE IS TO PROJECT, AND SAIDSHEET AND SAID TUBE BEING OF DISSIMILAR MATERIALS, BY ARC-WELDING WITH ANONCONSUMABLE ELECTRODE WHICH COMPRISES, POSITIONING SAID TUBE IN SAIDOPENING, PLACING A RING OF A FILLER MATERIAL WHICH PRODUCES SATISFACTORYJOINTS BETWEEN SAID DISSIMILAR MATERIALS AROUND SAID TUBE AT A POSITIONADJACENT SAID SHEET, POSITIONING SAID ELECTRODE AT A PREDETERMINED FIRSTANGLE TO THE AXIS OF SAID TUBE, AT A PREDETERMINED SECOND ANGLE INTRAILING RELATIONSHIP TO THE SUCCESSIVE PLANES PERPENDICULAR TO THEPLANE OF SAID OPENING AND INCLUDING THE AXIS OF SAID TUBE AND THESUCCESSIVE POINTS WHERE A WELDING ARC FROM SAID ELECTRODE IS TOTERMINATE AND WITH THE TIP OF SAID ELECTRODE A PREDETERMINED DISTANCEFROM THE OUTERMOST POINT OF SAID RING SUCH THAT A CONTINUOUS QUIETWELDING ARC MAY BE MAINTAINED BETWEEN SAID ELECTRODE AND SAID RING,MOVING SAID ELECTRODE ABOUT SAID AXIS WHILE MAINTAINING SAID ELECTRODESO POSITIONED, AND PRODUCING A WELDING ARC BETWEEN SAID ELECTRODE ANDSAID RING WHILE SAID ELECTRODE IS BEING SO MOVED TO WELD SAID RING ANDPRODUCE A SEAL BETWEEN SAID TUBE AND SHEET AT SAID JUNCTION, THE JOINTPRODUCED BY SAID WELD INCLUDING ONLY THE METAL OF SAID RING, THE METALOF SAID TUBE AND THE METAL OF SAID SHEET.